Knife sharpening device



July 30, 1940;

R. w. CUMMINGS 2209,1589

KNIFE SHARPENING DEVICE Filed March 1, 1938 2 Sheets-Sheet 1 y 1940- R.-w. CUMMINGS 4 2,269,389

KNIFE 'SHARPENING DEVICE Filed March 1, 1938 2 Sheets-Sheet 2 Patented July 30, 1940 UNITED STATES,

2,209,389 KNIFE SHARPENING DEVICE. Roy ,W. Cummings, Beverly, Mass, assignorto United Sh'oe Machinery Corporation, Borough of Flemington, 'N; J., a corporation 'of New Jersey e r i eiiqn Mar 1 Claim.

This invention relates to methods of sharpening and devices for use therewith andis herein illustrated as embodied in a devicefor sharpening the edge of a belt knife such as is used in certain 6' types of machines for splitting or eveningpieces of leather.

In the use of machines for this kind of work, it is often necessary to remove very thin layers of leather, sometimes as thin as one-thousandth of an inch. In order to do this work it is necessary that the knife be extremely sharp or keen to prevent its pulling and tearing the leather and it is difiicult to maintain a suitable cutting edge on the knife because such knives must be made of comparatively soft steel, substantially of the character from which band saws are made,

since they are subjected to the same running conditions of continual flexing around the circumferences of their driving pulleys. It is obvious therefore that, with such comparatively soft steel, the cutting edge will not retain its keenness for any great length of time. This makes frequent grindingnecessary and reduces the width of the knife rapidly to a point where it is no longer usable.

The knife is usually sharpened by means of a pair of grinding wheels, one operating uponone bevel of the knife and the other operating simultaneously upon the opposite bevel while the knife is driven longitudinally between them, the movement of the knife being the same as when the knife is operating to split leather. Therefore, any given portion of the knife is operated upon, 35 first by one, rinding wheel and then by the other one of the pair. The first wheel causes a burr to be formed onone side of the knife edge and the second wheel grinds off this burr but, in its place, produces a burr on the opposite bevel of the knife; therefore, in order to produce a suitable cutting edge, it, is necessary to hone the knife after grinding, in order. to remove the burrs and get a smooth cutting edge.

There is a further objection to the usual grind-v 45 ing operation because it frees particles of the abrasive which eventually may get into the VTQIK:

ing parts of thesplitting machine and cause excessive wear rota- 2 macetherein,

It isan object of thepresent inventionto pro;

50 vide a method of, and device for, sharpening such knives whieh. will produce an operative edge on the knifewithout the formation. of any, burrs, so that no honing is necessary.

It is another object ofthe invention to provide a sharpening method and device from which no Ill a S ia e .53

abrasive dust can be thrown into the working parts of the machine. I

It isa further object to provide a method and a device for this purpose in, which, during the process of sharpening, the edge on the knife will be hardened to resist wear and so permit longer intervals of use between knife sharpening opera-- tions. 1

In accordance with the objects of the invention, there is provided a methodiand' a device which will produce a cutting edge by a scraping action, using two sharp scraping edges of an extremely hard material, one on each side of the.

knife, these edges being. slightly separated from each other and displaced ata suitable angle.

When these edges are brought into contact with the moving knife they scrape, off material from the two bevels of the knife until-the knife edge is brought completely tothe. apex of the angle formed by the two scrapingedges. The knife is supportedor backed up at its opposite or back edge so that the material of the knife is crowded and compacted intov the apex of the angle be: tween the scraping edges and in this manner becomes somewhat harder at andclose to the edge than the remaining. portion of theknife. This hardened portion is. very near to the. neutral axis of the'knife so that, although it has been somewhat hardened, it will not break when the knife, is flexed. It is thus possible, by obtaining this hardened edge, to increase the life of the knife edgeover that of the usual edge obtained by grinding soft, steeL.

It should be noted,that, as, noabrasive isused inthe above method of sharpening with the device. provided therefor, there is no abrasive dust to get into the working parts-of the splitting machine and cause excessivewear.

The invention will be better understood when the followingspecification is considered in con: nection with the accompanying drawings, in which,

Fig. 1 is a side elevation, partlyin section, of the sharpening device, of the present invention and showing the knife of a belt knife splitting machine in cross-section and in operative relation to the sharpening or scraping tools of the device;

Fig. 2 is a plan View, partly in. cross-:section takenalong the line 11-11 of Fig. 1, and looldng in the direction of the arrows; v a

Fig. 3 is a front sectional view, taken along the line IIIIII ofv Fig. 1, looking in the direction of the arrows,' and showing the guideway on which ,the sharpening device is adjustably mounted;

Fig. 4 is an enlarged plan view, partly in section, of the tool holders and taken along the line IVIV of Fig. 1, looking in the direction of the arrows;

Fig. 5 is a view (on the same scale as Fig. 4) of the belt knife in transverse section, looking in the direction of the arrow B in Fig. 7 with the sharpening tools in operative position;

Fig. 6 is a transverse sectional view of the belt knife (on a still further enlarged scale), taken on the line VIVI of Fig. 2, looking in the direction of the arrows and showing the straight bevel of the knife after being sharpened with the sharpening device of the present invention and having indicated thereon for comparison, the shape of the curved bevel produced by the usual grinding wheels;

Fig. 7 is a plan view (on the same scale as Figs. 4 and 5) of the knife and sharpening tools partly in section and taken along the line VII-V11 of Fig. 5, and looking in the direction of the arrows, and is a simplification of Fig. 4;

Fig. 8 is an angular vertical cross-sectional view (on the same scale as Figs. 4, 5 and '7) of the knife and sharpening tools taken along the line VIIIVIII of Fig. 7 and looking in the direction of the arrows, and

Figs. 9 and 10 show details of construction.

The sharpening device is mounted on a base If] which is intended to be secured permanently in fixed position on the frame of the splitting machine whose knife is to be sharpened as occaslon requires.

The base I!) carries a head which, for ease of manufacture, is made in two pieces, l2 and I4, connected together, with provision for slight vertical adjustment, by a tongue-and-groove connection l6 and by screws l8. The head l2, I4, is mounted, for adjustment on the base l6, crosswise of the knife, in a dovetail slot provided with a gib 20 and handled adjusting screws 22. A feed screw 24 passes through a tapped hole in the lower part I2 of the head and this screw is carried in bearings in two vertical brackets 26 and 28 secured to the base In by screws 30. The feed screw 24 is prevented from moving longitudinally by two collars 32 and 34 which are pinned to reduced cylindrical portions of the feed screw. The collar 32 is provided with a graduated dial 36 whose position is indicated by an index mark located on the face of a projection 38 on the upper part of the bracket 26. The feed screw may be rotated by a crank arm 46 pinned to it and having a handle 42 secured to its outer end. The head l2, M, which carries the tools for sharpening the belt knife, as will hereinafter be described, can be accurately located, relatively to the knife, by turning the handle 42 and reading the dial 36 by means of the index mark. Thus, these tools may be accurately and firmly brought into the desired operative position, or may be moved free of the knife, by manipulating the handle 42.

The belt knife is sharpened, as stated above, by a pair of scraping tools, the upper one of which is designated 56 and the lower one 52. In order to produce the desired scraping action, the scrapingmaterial must be extremely hard and capable of being lapped to a high polish on the two surfaces that intersect to produce the scraping edge, so that the edge will be free from even the slightest suggestion of tool marks which would score the knife. Especially suited for use as scraping tools are cemented carbides, such as tungsten carbide, as sold under the trade name Carboloy. This material must be sharpened on a very fine diamond dust lap in order to obtain the above described desired finish. As this carbide is expensive and brittle, a small piece of it is welded to a steel supporting member to form a complete scraping tool with a Carboloy scraping edge. The Carboloy portions of the upper and lower scraping tools are designated respectively by the reference characters 54 and 56 having corresponding scraping edges 58 and 60.

From Fig. 7 it will be seen that the scraping edges 58 and 60 are located in contact with the entire width of the bevel faces 62 of the belt knife 63 at equal and opposite angles of (in plan View, i. e., as viewed in a direction normal to the plane of the knife) to the cutting edge 64 of the knife, i. e., to the path of movement of the knife. These scraping edges are shown in Fig. 7 as crossing each other at a: but they do not actually touch, being separated by the thickness of the knife just back of its edge. The scraping edges 58 and Bil of the tools are angularly displaced, as viewed in a vertical plane at right angles to the knife 63 as shown in Fig. 5, by the amount of the included angle of the bevel of the knife, the tools each making equal angles with the central plane of the knife. The lower face 68 of the upper scraping tool 56 and the upper face 16 of the lower tool 52 are beveled away from the blade of the knife for clearance so that only the scraping edges 58 and 66 of the tools make contact with the belt knife. As illustrated in Fig. 7, the scraping edges 58 and 66 make contact with the beveled faces of the knife at equal and opposite angles so that, as the belt knife moves in the direction of the arrow A (Fig. '7), the upper edge 58 tends to bite the knife and draw it laterally toward its cutting edge, while the lower scraping edge 60 makes an equal angle in the opposite direction which tends to draw the knife in the opposite direction to neutralize the first action. Accordingly there is no tendency for the scraping edges to move the belt knife laterally in either direction as it is drawn between the Carboloy tools.

Referring to Fig. 6, it should be noted that the straight edges of the scraping tools give flat bevels 62 to the splitting knife. These bevels give a cutting edge much stronger at the cutting point than the concave bevels (indicated by dot and dash lines produced by the usual grinding wheels.

When the scraping tools are fed against the belt-knife by turning the handle 42, it is necessary to provide an unyielding resistance to lateral movement of the knife to receive the thrust of the scraping tools so that they will be effective to sharpen the knife. To the above end, the back of the knife is supported by the bottom of a thrust-receiving groove 14 in an adjustable block 16. (Shown in detail in Fig. 9.)

This block 16 is provided with a round shank 16 adjustably mounted in an upward extension 86 of the bracket 28 and is thus. after adjustment of the two nuts 82, 82, secured in fixed position relatively to the path of travel of the belt knife As a knife passes through the sharpening device, it is also guided vertically between an upper plate 85 and a lower plate 86 secured respectively to the two parts l4 and I2 of the head. The space between the plates may be adjusted by adjusting the parts l4 and I2 in the dovetail slot l6 and clamping them in position by the screws [8.

The upper portion I4 and the lower portion [2 of the head are respectively provided with bores 90 and 92. In these bores are mounted, respectively, tool holders 94 and, 95 which may be suitably adjusted to position'the tools in the previously described proper relative operating positions with respect to each other and with respect to the belt knife $3. These holders are identical in construction and are mounted in a similar manner. Accordingly only the upper holder 94 will be described in detail.

The upper scraping tool 50 is secured in a rectangular socket in the lower endof the tool holder 9 by means of two set screws 100 located at right angles to each other so that the, tool 50 and holder 95 move as a unit to any desired adjusted position.

The tool holder is provided with two diametrically opposite keys I82 and H34 which slidingly fit .keyways cut in the bore 90.

$4 is thus prevented from turning when vertical adjustments are made. To make such adjustments, an adjusting screw I06 is tapped in the upper head member Hi (coaxial with the bore 90). The lower end of the adjusting screw is reduced in diameter in three places to provide two alined cylindrical surfaces H38 and H0, separated by a grooved portion H2. A diametrically split washer lid (see Fig. is positioned in the groove H2 and, at the same time, in a counterbore in the top of the tool holder 94. The Washer is clamped in the tool holder by means of a threaded thimble H6 which thimble is screwed into the tool holder 9d. The adjusting screw and tool holder are thus secured together for relative rotation, without axial movement, so that, by turning the adjusting screw Hi6, the tool holder may be raised or lowered. A lock nut I I8 is positioned on the screw to lock the holder in adjusted position.

The lower tool holder 96 is similarly adjusted to bring it into proper adjusted position as to height by the adjusting screw I20. The proper The tool holder adjusted position for both holders is such that equal amounts of material are removed by each scraping tool, so that the cutting edge of the belt knife will remain located in its median plane, thickness-wise.

Whenever vtheknife needs to be resharpened, the handle 42 is turned to bring the scraping tools into contact with the knife as it is being driven past them. Then the handle is-turned further just sufficiently to remove enough material from the knife to bring it to the desired keen cutting edge. Further, when the scraping tools themselves become dull, the head l2, I4 can be moved forward by means of the handle 42 and the tools readjusted vertically to the above-described median plane position by the adjusting screws HlB and I20 to obtain new portions of the scraping edges for operative engagement with the belt knife. After the scraping tools become dull throughout their length, they may be removed and re-lapped with diamond dustto produce new polished surfaces which intersect to form a new and sharp scraping edge.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

A belt-knife sharpening device having, in combination, a base, a head adjustably carried by the base, means mounted in the headfor guiding a portion of the knife and for supporting the back of the knife, two tools also mounted in the head, said tools having straight scraping edges which cross each other without being in contact and are positioned at substantially equal angles with the edge of the knife as viewed in a direction normal to the plane of the knife, means for adjusting each tool independently'of the other toward and from the knife in a path which is substantially perpendicular to the plane of the knife, and means for adjusting the head on the base in a path which is parallel to the plane of the knife and transverse to its cutting edge.

ROY W. CUMMINGS. 

